High-voltage-measuring instrument.



J. B. WHITEHEAD.

HIGH VOLTAGE MEASURING INSTRUMENT.

APPLICATION FILED APR.5, 1912.

1,059,095. Patented Apr. 15, 1913.

aooooooo Fooooooo l I 3 JOHN B. WHITEHEAD, QF BALTIMORE, MARYLAND.

HIGH-VOLTAGE-MEASUBTNG INSTRUMENT.

Specification of Letters Patent.

Patented Apr. 15, 1913.

Application filed April 5. 1812. Serial No. 688,758.

2?" all whom g't may concern Be it known that 1, JOHN B. WHITEHEAD, a "citizen of the United States, residing at Baltimore city, State of Maryland, have invented certain new and useful Improvements in High-Voltage-Measuring Instrumerits, of which the following is a specification.

This invention relates to an apparatus for the measurement of high voltages, andis based on the fact that a visible discharge, or corona forms on a high volt-age'wire in air at a perfectly definite electric stress, and this stress depends in a definite way on the diameter of the wire. Corrections for temperature and pressure are easily applied.

The presence of corona indicates that the air ceases to insulate and that a leakage or powerless is present. This invention also so makes use of the fact, to indicate the presence of the corona, that'visihle corona is accorncanied by ionization f and consequent conductivity of the surrounding air.

Aside from purely laboratory use, the invention has application in a practical way in the measurement of high voltage in many cases in. which the methods at present in use do not permit of accurate determination. As an example of such practical application, I might mention the testing of insulation in high voltage apparatus. This, however, as well as many other points, will be gone into in greater detail in the description to follow.

in order to more fully describe my said lid L; one :t'orrn of instrument embodying my id invention; F 1g. 2 represents in side elei t on, one of the forms in which the inte conductor may be made; Fig. 3, an- :r form which the interior conductor he Fig. 4, a fragmentary front -on of a form of the instrument enia; d with interior conductor of graduated er; 5, a section taken on line .1 F 1g. a a detail central-secan eye piece; Fig. 6', a frag y sectional semi-diagrammatic view another form of instrument embodying my said invention; and Fig. 7, a diagram illustrating one of the practical applications of my invention.

in the form of the instrument as shown in Fig. l, 1 represents a conductor, circular in cross section and of a diameter which has tion, reference will be had to the acbeen found to correspond to a given critical surface intensity; that is, to the voltage gradient at the surface of the conductor at which visible corona appears and ionization of the neighboring air with accompanying conductivity be us. With a, given size of outer cylinder t e relation between the voltage applied between the c linder and the w re, and the resulting sur ace intensity or gradient, in volts per centimeter, is. given by the expression where E is the surface intensity as stated above, V is the voltage in volts and 4' and which the conductor 1 is supported, in the case shown as follows :-The conductor eX- collaror bushing 3, which is slidable on the said conductor, but is made fast thereto by a set screw 42. At its other end, the said conductor 1 passes through an elongated metal sleeve or bushing 5 which it fits tightly and to which it is made fast by soldaring or otherwise. The. bushings 3 and Ellie respectively within fixed metal bushings 6 and 7 which extend through two central alined openings in two insulating caps 8 and 9 on the ends of the tube 2. The conductorl is drawn taut by means of a nut 10, screw threaded on the bushing 53, as shown, the upper end of the conductor being held rigidly by the bushing 3 which is providedwith a head 11 which, being on the top of the bushing .6 resists the downward pull of the conductor.

The presence of the corona in rectly visually, and second by means of an instrument responsive to the presence of the corona. For detecting the presence of the corona surrounding the conductor 1, in a this instrument may be detected in. two ways; first dilocated at any other desired point so long as they permit of sight of the conductor 1 within the tube 2.

For detecting the presence of the corona by means of an indicating device responsive thereto, in the case of the form of the instrumentshown in Fig. 1, I provide .at any desired position on the cylinder 2 a series of openings 14 through the wall of said cylinder, and locate just outside of these openings a conductor 15 which may be a small coil of wire which connects to a go d leaf electroscope 16, the said wire and electroscope being incased in a suitable box or housing 17 and the conductor 15 supported in an insulating bushing 18.

Each instrument may be supplied with I any desired number of Wires .1 of difiering the insulation of this armature. Such a case is illustrated in the diagram Fig. 7. where 19 represents the armature being tested, 20 a transformer, 21 a voltage regulator connected between the primary of said transformer and a source of electromotive force 22. In such a case, the voltage to be determined is appliedbetween the conductor 1 and the tube 2 of my instrument. Fig. 7 merely indicates these connections diagranr matically, though the instrument may be provided withterminal binding posts for making these connections. The voltage is then run up unt-ilthe corona forms around the conductor 1. It is known that this corona forms around the selected conductor at a certain voltage. Therefore by merely observing the presence of this corona, the voltage becomes known. As stated above, this presence may be observed visually as described, or by means of an indicating instrument. To observe the presence of corona visually, however,'requires that the instrument be in a dark room; whereas observation by means of an electroscope or other indicating instrument may be carried on anywhere. i

The operation of the electroscope is due to the presence of ionization accompanying the forl'nation of the corona. In the operation of the instrument, the electroscope is initially charged by any one of several well known methods, the electrode 15 being provided for this purpose. Then, under the presence of ionization, accompanying the through the medium of ionization by means of an indicating instrument responsive thereto, and I believe that I am also the first to show the degree of accuracy, namely to a fraction of one er cent, with which the visible corona int icates the critical voltage.

For determining another voltage with the form of instrument shown in Fig. 1, another wire would be placed in the instrument, and so on for the various volagcs to be determined, each such instrumcnt being preferably provided with a. number of calibrated wires.

- Instead, however, of providing each instrument with a plurality of wires 1, each corresponding to a predetermined voltage, I may provide a single conductor for a number of different voltages by making the conductor of graduated diameter. For example,

it may be a conical cmiduetor 1, or a. stepped conductor 1". In the case of the conical conductor, various points may be marked on the cylinder 2, correspontlirrg to the voltage at which. corona forms on a wire of diameter the same as that opposite the marked point. By thus noting the point on this conductor where the corona appears, the voltage may be determined. The marks 21 indicate the various voltages for which the wire has been calibrated.

In the case of the stepped :onductor, Fig. 3,'each separate diameter corresponds to a given voltage at which corona forms on that portion of the conductor, and by merely 5 noting the presence oi. corona on any of these sections, the voltage is known.

Of course, when the conical or stopped conductor is used, the means for detecting the corona must be adjustable lmigitudinally of the conductor. For this purpose, the tube 2 may be provided with a row of openings 25 extending longitudinally of the tube, in which case the peep hole or the. conductor 15 and elcctroscope may be slidahle longitudinally of said tube in any desired way. In the case of the conductor 15, this may be effected by providing t e housing 17, inclosing the electroscope 16 and con ill) ductor 15, with side flanges 26 whichcngage and slide in guides 27 and 28, fixed to the cylinder 2. See Figs. 4 and 5.

The holes 25 may be used also for observing the corona visually, in which case an eye piece 13 provided with flanges 26 adapted to fit the guides 27 and 528, may be substituted for the indicating instrument.

in Fig. 6, I have shown the substitution of a galvanometcr for an elcctroscopc, and

have also shown a diil'erent form of elec- 1 trode from that indicated by the numeral 15 in Fig. 1. ln 6, the tube 2 corresponds to the tube 2, Fig. 1, except that thetube 2* is provided with a belt of openings is extending entirely around the cylinder.

Surrounding. this belt of openings, is a metal collar or belt 29 which takes the place of electrode 15. This electrode 29 is held by supports 30, made fast in insulating bushings 31 in a metal casing 32. 'Connected series between the electrode 29'andeartln'are a galvanometer 33 and a battery or other source of continuous potential 34, The cylinder 2 is grounded as at 35.

in this way, the galvanoineter is made readily responsive, through the medium of ionization, to the presence of the corona. it should be understood, however, that the form of electrode 29, Fig. 6, works well also with an electroscope and may be so used, and that the form of electrode 15 may be used with: the galvano-meter'.

The corrections for temperature and pressure, which have been worked out experimentally, would be supplied with each instrument, either in the form of multiplying factors of'the observed critical voltages,-or in the form of curves.

Without limiting my invention to the speoitlc forms thereof herein'shown' and dcscribed, what I claim is l. A high voltage measuring instrument,

comprising two concentric conductors, one of which a diameter corresponding to a given critical intensity, substantially as cribed. A high voltage measuring instrument, comprising two concentric conductors, one of whi as a diameter corresponding to a given or cical surface intensity, and indicating means responsive to the presence of co, ronasurrounding the last named conductor, substantially described.

3. A high voltage measuring instrument, comprising two conductors one of which has a diameter corresponding to a given critical surface intensity, and indicating means responsive to ionization set up by the formationof corona about the last named conductor, substantially as described.

4;. A high voltage measuring instrument, comprising two conductors, one of which has a diameter corresponding to a known critical surface intensity, and indicating means comprising an electroscope'responsive to ionization set up by corona formed about the last named conductor, substantially as described.

5. A high voltage measuring? instrument, comprising two concentric conductors, one of which. is ct graduated diameterlcorrespending to known critical surface intensities, su stantially as described.

6. A high voltage measuring instrument, comprising a cylinder of, electrical conducting material, insulating caps on its ends, removable bushings centered in said caps in alinement with each other, and an electrical conductor mounted in said bushings and concentric with said cylinder, the said conductor having a diameter corresponding to a given critical surface intensity, substantially as described.

7. A high voltage measuring instrument, comprising a cylinder of electrical conducts ing material having one or more openings through its side, an electrical conductor concentrically mounted within said cylinder and extending longitudinally thereof, insulating supports for said conductor, an electrode adjacent said openings outside of said cylinder, and indicating means connected to said electrode and responsive to the presence of corona formed about said conductor with: in said cylinder, substantially as described.

8. A high voltage measuring instrument, comprising a cylinder of electrical conducting material, an electrical conductor having a diameter corresponding to a known critical surface intensity and mounted within said cylinder, concentrically therewith, the said cylinder having one or more openings for the detection of the presence ofcorona about said conductor, substantially as dcscribed.

9. A high voltage measuring instrument, comprising a cylinder of electricalcondizcb ingmaterial having a row of holes in its side extending longitudinally thereof, an electrical conductor of graduated diameter corresponding to known critical surface in tensities and mounted Within said cylinder concentrically therewith, and means ,respoir sive to the presence of corona about said conductor, adjustably mounted for move ment longitudinally of said tube in front of said openings, substantially as described.

10. A high voltage measuring instrument, comprising a cylinder of electrical conducting material, insulating caps over its ends, bushings centered in said caps, a conductor extending through said bushings axially of said cylinder and made last to said bushings, the said conductor having a diameter correspondin to a known critical surface intensity, and means coiiperating with said bushings to draw said conductor taut, substantially as described.

In testimony whereof I afiix my signature in presence bf two witnesses.

JOHN B. WHITEHEAD.

Witnesses WM. H. YEATMAN, J osnrH A. NEUM'ALNN. 

